All you should need is the Windows sound drivers. If your codecs are messed up, from experience, that's a pretty tough issue to reverse. Are you overclocked at all on your machine? I had an issue with CryEngine where it was not correctly detecting the final CPU speed and so the real time clock it accessed was inaccurate causing the audio to lag and skip during cutscenes and gameplay. It also caused certain animations to be mistimed.

Yesterday I flashed the BIOS, still got skipping in Crysis music, the final scene was laggy, it was really weird, the sound was skipping and then the graphics started skipping too, I barely completed the game, think I got 5 fps on the run to the vtol.

I feel like tossing my computer out the window, I can't seem to play anything without problems.

Update : I just checked Deus Ex, the cutscenes are no longer skipping, I'm so happy.